Hi,
i just emerged netatalk and configured it
i started atalkd/afpd and tried to connect from my mac. It connects and authentifies fine, even mount the disk (if i'm fast to click ok) and then the server (afpd) cut the connection.
here the log:

assign a passwd with afppassword to you user!!
altough PAM will allow the access without the password setup then something probably goes wrong (i have no idea of what since it worked on my debian and i'm not sure of the way pam operates exactly... :/)